• Refine Query
  • Source
  • Publication year
  • to
  • Language
  • 16
  • 10
  • Tagged with
  • 26
  • 26
  • 26
  • 26
  • 26
  • 26
  • 6
  • 5
  • 5
  • 5
  • 4
  • 4
  • 4
  • 4
  • 3
  • About
  • The Global ETD Search service is a free service for researchers to find electronic theses and dissertations. This service is provided by the Networked Digital Library of Theses and Dissertations.
    Our metadata is collected from universities around the world. If you manage a university/consortium/country archive and want to be added, details can be found on the NDLTD website.
11

Restoration of a Rich Fen by Top Soil Removal : Temporal and Spatial Responses among Vascular Plants, Bryophytes and Land Snails during 15 years

Evasdotter, Liselott January 2011 (has links)
Rich fens are calcareous and nutrient poor wetlands with a rich flora of orchids, sedges and mosses. As many as one hundred plant species are rich fen specialists. Many wetlands have been drained historically, and transformed to agricultural land or production forests. Today rich fens cover only 2-3% of the total mire area in Sweden. Rich fen is a rare and valuable habitat also from a European perspective and is protected in the Natura 2000-network. To increase and maintain the biodiversity and ecosystem services rich fens can offer, it is important to increase the rich fen area by restoration and management. Rich fen restoration can be carried out in different ways. In this report the restoration method of top soil removal is investigated. The method has never been tested before in Sweden and therefore it is important to evaluate the suitability of the method for further conservation work.   Before restoration, the study area had been drained, used as arable land and pasture, and finally become abandoned and overgrown by tall eutrophic herbaceous vegetation. An excavator dug away the layer of nutrient rich top soil and then the site was left for spontaneous development. Adjacent to the restored area, there is a small remnant of rich fen. Monitoring of the restored area was performed during the first five years after the restoration. I repeated the monitoring after ten years, and analyzed the long-term succession of plants and snails, in comparison with the status in the reference fen.   The vegetation in the restored parts is approaching the one in the reference fen. For example, the number of rich fen specialists has increased steadily. However, the colonization of bryophytes is slow. They cover at most 20 % in the restored parts, while 80 % in the reference fen, possibly because of dispersal limitation and the fact that the restored area is drier than the reference fen. More species of herbs can be found in the restored parts than in the reference fen. Another difference is the high cover of bare soil in the restored areas, compared to none in the reference fen. Some trees and bushes are growing in the area, primarily birch (Betula pubescens) and different species of Salix. The land snails have successfully colonized the restored areas. After two years the same number of species was found in the restored area, as in the reference fen. The total number of species found in the restored areas was 26, compared to 29 in the reference fen, among them three rare rich fen indicator species.   The results show how the restored site has developed from bare mineral soil to a rich fen site, approaching the species composition of the reference fen. Several species of rich fen specialists among vascular plants, bryophytes and land snails have established in the restored areas. The small rich fen close to the restored area functions as a source from where plants and animals can spread. Overall the restoration shows very positive results, going from bare soil to rich fen vegetation in only ten years.
12

Towards a Sustainable Fisheries Management : How to address uncertainty in order to achieve a sustainable development of regional fisheries management

Folkesson, Malin January 2010 (has links)
Fisheries management is not only about managing the resource fish, but also includes managing the social system. Aquatic ecosystems and the social system are both complex and change continuously. It is important to address what types of uncertainty the combination of both systems, complex socio-ecological systems leads to, their consequences and how these should be dealt with. Successful or unsuccessful management outcomes are difficult to address whether or not they are due to management efforts or natural changes. In addition, uncertainties often lead to a short-term management, since lack of knowledge makes it difficult to act in a long-term perspective. This thesis conceptualizes how to address different types of uncertainty prevalent in fisheries management, with focus on natural process uncertainty, measurement and estimation uncertainty, decision and implementation uncertainty, and institutional and regime uncertainty.  This was done by analyzing how three theoretical approaches, namely co-management, adaptive management and adaptive co-management address these uncertainties. In order to highlight how different types of uncertainty have been dealt with in practice, a case study on the fishery management in Lake Vättern has been made. A comparison between the literature study and this thesis’ case study shows that hypothesis-testing, cooperation, communication and transparency are corresponding factors on how to deal with uncertainties in fisheries management and that institutional and regime uncertainty is inadequately addressed in Sweden.
13

Metapopulation persistence of insects living in hollow oaks: effects of adding oaks in  the surrounding landscape

Gilljam, David January 2009 (has links)
<p>The oak district of Östergötland is one of the largest oak forests left in Europe and it harbours many threatened species dependent on old hollow trees. In this study, the saproxylic beetle <em>Osmoderma eremita</em> living in hollow oaks was used as a model species and parameterised for a metapopulation model (the incidence function model) at the level of individual trees. The aim was to set up a number of conservation management scenarios, where new oaks were added to increase the quality of the matrix and then simulate the resulting metapopulation occupancy, using three levels of dispersal. A real data set of hollow oaks was used as the base for modeling. Oaks were added to cells in a lattice covering the study landscape, where cell size, cell position and numbers of oaks per hectare were varied. The results show that a larger area of added oaks and a greater number of oaks per hectare will give a higher increase in total occupancy, no matter the dispersal, but the second smallest cell size used (3.4 km2 ) will give the highest response per effort for medium and high dispersal abilities, and smaller cells with greater number of oaks per area can be more effective. The spatial position of the increase in occupancy differs depending on dispersal ability of the focal species and should be considered in conservation management work. For unoccupied cells, the effort required to get the cell occupied will be smaller for cells having a greater number of oaks.</p>
14

Participatory watershed management to decrease land degradation and sediment transport in Kagera and Nyando catchments of Lake Victoria basin

Kenge, James Gunya January 2009 (has links)
<p>Attention to participatory watershed management is increasing across the developing world<em> </em>as<em> </em>soil erosion continues to degrade agricultural land; reservoirs and irrigation infrastructure are clogged with sediment. The realization of the importance of watersheds is crucial for sustainable utilization especially in developing countries where rural livelihoods and economies are highly dependant on the exploitation of natural resources. The Lake Victoria basin is characterized by high population pressures, low productive subsistence agriculture, poor farming methods, loss of soil fertility and deforestation due to demand of fuel wood and charcoal, timber and building materials that are posing serious threat to watersheds. High population density in the basin also means new needs emerge too fast to which rural societies cannot respond in time leading to more area expansion for agricultural land. In spite of positive efforts under the Lake Victoria Basin Commission, there remains a huge gap between policy and institutional framework development at the top level and the actual implementation of actions on the ground to prevent land degradation, soil erosion and decrease sediment load. The study focused on Kagera and Nyando catchments of Lake Victoria Basin and aiming to establish if there exist and the extent to which participatory watershed management has been implemented on the ground to decrease land degradation and sediment load. It therefore provides an insight into watershed management in the Kagera and Nyando catchments by illustrating the link between policy formulation and actual implementation and enforcement.</p>
15

Metapopulation persistence of insects living in hollow oaks: effects of adding oaks in  the surrounding landscape

Gilljam, David January 2009 (has links)
The oak district of Östergötland is one of the largest oak forests left in Europe and it harbours many threatened species dependent on old hollow trees. In this study, the saproxylic beetle Osmoderma eremita living in hollow oaks was used as a model species and parameterised for a metapopulation model (the incidence function model) at the level of individual trees. The aim was to set up a number of conservation management scenarios, where new oaks were added to increase the quality of the matrix and then simulate the resulting metapopulation occupancy, using three levels of dispersal. A real data set of hollow oaks was used as the base for modeling. Oaks were added to cells in a lattice covering the study landscape, where cell size, cell position and numbers of oaks per hectare were varied. The results show that a larger area of added oaks and a greater number of oaks per hectare will give a higher increase in total occupancy, no matter the dispersal, but the second smallest cell size used (3.4 km2 ) will give the highest response per effort for medium and high dispersal abilities, and smaller cells with greater number of oaks per area can be more effective. The spatial position of the increase in occupancy differs depending on dispersal ability of the focal species and should be considered in conservation management work. For unoccupied cells, the effort required to get the cell occupied will be smaller for cells having a greater number of oaks.
16

Participatory watershed management to decrease land degradation and sediment transport in Kagera and Nyando catchments of Lake Victoria basin

Kenge, James Gunya January 2009 (has links)
Attention to participatory watershed management is increasing across the developing world as soil erosion continues to degrade agricultural land; reservoirs and irrigation infrastructure are clogged with sediment. The realization of the importance of watersheds is crucial for sustainable utilization especially in developing countries where rural livelihoods and economies are highly dependant on the exploitation of natural resources. The Lake Victoria basin is characterized by high population pressures, low productive subsistence agriculture, poor farming methods, loss of soil fertility and deforestation due to demand of fuel wood and charcoal, timber and building materials that are posing serious threat to watersheds. High population density in the basin also means new needs emerge too fast to which rural societies cannot respond in time leading to more area expansion for agricultural land. In spite of positive efforts under the Lake Victoria Basin Commission, there remains a huge gap between policy and institutional framework development at the top level and the actual implementation of actions on the ground to prevent land degradation, soil erosion and decrease sediment load. The study focused on Kagera and Nyando catchments of Lake Victoria Basin and aiming to establish if there exist and the extent to which participatory watershed management has been implemented on the ground to decrease land degradation and sediment load. It therefore provides an insight into watershed management in the Kagera and Nyando catchments by illustrating the link between policy formulation and actual implementation and enforcement.
17

Ekologiskt Hållbar Turism : En nisch för naturens bästa

Pitkänen, Kim January 2011 (has links)
Det är allmänt känt att turismen för med sig negativa ekologiska konsekvenser och har gjort det sedan charterturismen på allvar slog igenom under -50 och 60-talet. På senare tid har alternativ turism börjat gro och tagit sig upp. Att massturismen är dominerande råder det inga tvivel om men det är viktigt att alternativ turism såsom ekoturism ser dagens solljus, en nisch i turismen som ska vara ekologiskt hållbar. Vandringen mot toppen är lång och brant för den ekologiskt hållbara turismen, nyligen har den börjat se dagsljuset men massturismen tar åt sig nästan all energi från solljuset. Det innebär att den ekologiskt hållbara turismen måste kämpa i hård konkurrens med de andra aktörerna på marknaden. Aktörer som i dagsläget och även i fortsättningen kommer vara starkare, men det säger inte att det inte finns plats för ekologiskt hållbar turism. Uppsatsen visar att det finns ett bra utbud av litteratur om ekoturism som tar upp både skrämmande exempel där varumärket utnyttjats till skadligare verksamhet och exempel med rätt använd ekoturism som ett verktyg för värnande av biologisk mångfald. Den litterära granskningen redogör för betydelsen av ekologiskt hållbar turism och vad som kan göras för att nå dit. En enkätundersökning gjordes i sydvästra Sverige med syfte att ta reda på hur folket ser på ekologiskt hållbar turism. Vissa intressanta skillnader fanns mellan personer av samma kön och kvinnor gentemot män, men glädjande var att de flesta av dem 136 svarande trodde eller hoppades att den ekologiskt hållbara turismen har en ljus framtid att gå till mötes. I Sverige har vi idag 81 av Naturens Bästa godkända ekoturistarrangörer. Trots skuggan från de större verksamheterna verkar det finnas tillräckligt med ljus och plats för den ekologiskt hållbar turismen att slå sig in på marknaden.
18

DETERMINATION OF FREE STAND-ALONE PHOTOVOLTAIC POTENTIAL IN GERMANY BY GIS-BASED SITE RANKING

Shoshtari, Salahaldin January 2010 (has links)
<p>The purpose of this study is to find potential areas suitable for energy production using renewable sources. For this aim, accurate assessments are necessary. The assessments include geographical suitability, closeness of infrastructure and observing local and regional framework concerning the use of renewable sources together with environmental protection. In addition, economical factor is considered in such an assessment. In this study, the Photovoltaic (PV) production potential for Germany is considered. An accurate and complete data set is necessary in order to achieve reliable results. In addition, a powerful database management and strong analysis tools are required. Geographical Information System (GIS) is a tool for finding suitable sites for the photovoltaic production.Using GIS, energy generation planners are able to visualize solar densities throughout the considered area. In addition, they can find the optimal and most economical sites by the combination of solar potential with the information about land. In this study, data sources consist of meteorological and geographical conditions. Furthermore, all analyses have been performed using Arc GIS Desktop. This study demonstrates the possible places for photovoltaic plants and indicates suitable candidates according to weights and factors in multi criteria analysis. The solar radiation data is from year 1995 to 2005. Land cover data is according to Corine 2000 and the more detailed Raumordnungskataster (Rok) for Weser-Ems. Numerical results are reliable from a comparison point of view. This study demonstrates the sensitivity of the defined criteria with respect to electricity production. In particular, this study is useful to see the capabilities of GIS for site selection regarding photovoltaic plants.The purpose of this study is to find potential areas suitable for energy production using renewable sources. For this aim, accurate assessments are necessary. The assessments include geographical suitability, closeness of infrastructure and observing local and regional framework concerning the use of renewable sources together with environmental protection. In addition, economical factor is considered in such an assessment. In this study, the Photovoltaic (PV) production potential for Germany is considered. An accurate and complete data set is necessary in order to achieve reliable results. In addition, a powerful database management and strong analysis tools are required. Geographical Information System (GIS) is a tool for finding suitable sites for the photovoltaic production.Using GIS, energy generation planners are able to visualize solar densities throughout the considered area. In addition, they can find the optimal and most economical sites by the combination of solar potential with the information about land. In this study, data sources consist of meteorological and geographical conditions. Furthermore, all analyses have been performed using Arc GIS Desktop. This study demonstrates the possible places for photovoltaic plants and indicates suitable candidates according to weights and factors in multi criteria analysis. The solar radiation data is from year 1995 to 2005. Land cover data is according to Corine 2000 and the more detailed Raumordnungskataster (Rok) for Weser-Ems. Numerical results are reliable from a comparison point of view. This study demonstrates the sensitivity of the defined criteria with respect to electricity production. In particular, this study is useful to see the capabilities of GIS for site selection regarding photovoltaic plants.</p>
19

Kommunalt naturskydd som en del av markanvändningsplaneringen : en fallstudie av olika synsätt i samband med upphävande av naturreservat

Bergkvist, Tomas January 2007 (has links)
<p>In metropolitan areas where the exploitation pressure increases, also the importance to point out nature areas grows, both for the sake of outdoor life and for biodiversity conservation. Since nature conservancy and spatial planning constitute two different parts of the municipalities land use control, a case study has been carried out in two municipalities in the Stockholm region, Huddinge and Järfälla. Both these municipalities have protected about one third of their land and today there are plans to repeal parts of the reserves to enable exploitation. This thesis shows – from the theoretical concept of sustainable development – officials, politicians and non-governmental organizations perspectives on questions concerning land use together with the work with nature reserves and repeals. The study focuses on how different basic attitudes and paradigms emphasizes different aspects of sustainable development and how this in turn affects the work to repeal nature reserves. Interviews with stakeholders in the municipalities and documents concerning land use and nature reserves demonstrates that there is distinct differences between the planning-paradigm, based on spatial planning, and the environmental-paradigm, based on nature conservation. From the planning-paradigm it is considered that nature reserves had to big impact on the munici­pality's land use and that valuable nature more frequently should be protected by the Swedish planning and building act. From the environmental-paradigms view the nature conservancy is – and should also in the future be – an important tool in the long-term prevention to stop valuable nature from being exploited. The thesis also stresses the importance to in the work with repeals take all effects that this kind of decision can lead to into account – not just in the repealed area but also for the future work with nature reserves on the whole.</p> / <p>I storstadsregioner där exploateringstrycket blir allt större, ökar också vikten av att peka ut naturområden, både för det rörliga friluftslivet samt för bevarande av den biologiska mångfalden. Utifrån det att naturskydd samt fysisk planering utgör varsin del av kommuners styrning av mark­användningen har en fallstudie genomförts i två kommuner i Stockholmsregionen, Huddinge och Järfälla. Båda dessa kommuner har skyddat ungefär en tredjedel av kommunens mark och idag finns planer på att upphäva delar av reservaten för att där möjliggöra exploatering. Uppsatsen visar – utifrån det teoretiska begreppet hållbar utveckling – hur tjänstemän, politiker och intresse­organisationer ser på markanvändningsfrågor samt arbetet med naturreservat och upphävande. Studien fokuserar på hur olika grundinställningar och paradigm lyfter fram olika aspekter av hållbar utveckling samt hur detta i sin tur påverkar arbetet med att upphäva naturreservat. Intervjuer med kommunala aktörer samt dokument rörande markanvändning och naturreservat visar att det finns tydliga skillnader mellan planparadigmet, med grund i den fysiska planeringen, och miljö­paradigmet, med grund i naturvården. Utifrån planparadigmet anser man att naturreservaten har fått för stor inverkan på kommunens markanvändning och att värdefull natur oftare borde skyddas med hjälp av plan- och bygglagens verktyg. Från miljöparadigmets vinkel är naturskyddet – och bör även i fortsättningen vara – ett viktigt verktyg för att långsiktigt förhindra att värdefull natur exploateras. Uppsatsen framhåller också vikten av att man vid upphävande av naturreservat tar hänsyn till alla effekter som ett sådant beslut kan leda till – inte bara i det upphävda området utan även för det fortsatta arbetet med naturreservat i stort.</p>
20

Effekter av upphörd hävd i Lurö skärgård : Har diversiteten av kärlväxtarter förändrats? / Effects of abandoned management in the Lurö archipelago : Are there any changes in the diversity of plants?

Thor, Annelie January 2008 (has links)
<p>One of the main reasons for the massive loss in plant species diversity is the fragmentation of habitats. In Europe, open pastures and meadows are the habitats going through the most changes during the 20th century, according to the agricultural changes. In this study vascular plants were invented at five different islands in the Lurö archipelago, Vänern, Sweden. The aim of the study was to sort out whether the diversity of plants has gone through any changes in abandoned managed grasslands compared to continuous managed grasslands. The aim was also to study if a change in the landscape has made any differences for the species development or decline. The results indicate that the number of vascular plants were significantly lower in the abandoned areas than the still managed areas. Results, only from the field layer, showed same results. There was a significant difference between the number of indicators in managed lands than lands that were abandoned for 30-40 and 100 years ago. A comparison from earlier study, from a time when grazing had just ceased at some islands, showed a significant difference in plant species diversity between the years. Just a few decades can impoverish a plant community that might have taken hundreds or even thousands of years to build up. To preserve the biological diversity formed by human impact, one must continue managing the lands.</p> / <p>En av de största orsakerna till den massiva förlusten av växtarter, är fragmenteringen av habitat. I Europa är öppna naturbetesmarker och ängar de habitat som genomgått de största förändringarna i och med jordbrukslandskapets omstruktureringar under 1900-talet. I den här studien inventerades kärlväxter på 5 olika öar i kulturlandskapet Lurö skärgårds naturreservat. Syftet var att ta reda på hur diversiteten bland kärlväxtarter skiljer sig mellan hävdade gräsmarker och f.d. gräsmarker där hävd upphört och hur ett förändrat landskap spelat roll för artantalets utveckling eller tillbakagång. Resultat visade att antalet kärlväxter var signifikant lägre i marker som slutat hävdas, än marker som fortfarande hävdas. Även jämförelser i enbart fältskiktet visade ett signifikant högre artantal hos välhävdade marker än marker där hävd upphört. Det fanns en signifikant skillnad mellan antalet indikatorarter i marker som var under hävd och marker som slutat hävdas för 30-40 år sedan, kontra 100 år sedan. Vid jämförelser med en tidigare studie, som ägt rum precis efter att hävden upphört på ett flertal lokaler visade resultat att det fanns en signifikant skillnad i artantal mellan de båda åren. På några få decennier kan ett helt växtsamhälle som byggts upp under hundratals eller kanske till och med tusentals år utarmas. För att bevara den biologiska mångfald som formas av en störningsregim beroende av människans inverkan, måste hävd fortsätta kontinuerligt.</p>

Page generated in 0.1626 seconds